Variable height boring type continuous mining machine



Feb. 26, 1957 I F. CARTLIDGE 2,783,037

VARIABLE HEIGHT BORING TYPE CONTINUOUS MINING MACHINE Filed Sept. 27, 1954 6 Sheets-Sheet 1 INVENTOR BY 4 W zATTORNEY FRANK CARTUDGE' I Feb. 26, 1957 F. CARTLIDGE VARIABLE HEIGHT BORING TYPE CONTINUOUS MINING MACHINE 6 Sheets-Sheet 2 7 Filed Sept. 27, 1954 N GHL INVENTOR FRANK B CAR FUDGE Y Q 4. M

' ATTORNEY Feb. 26, 1957 cARTLlDGE 2,783,037

VARIABLE HEIGHT BORING TYPE CONTINUOUS MINING MACHINE 6 Sheets-Sheet 3 Fiied Sept. 27, 1954 INVENTOR FRANK CARTLHDG'E B Y W" WWATTQRNEY FIG. 6

Feb. 26, 1957 F. CARTLlDGE VARIABLE HEIGHT BORING TYPE CONTINUOUS MINING MACHINE Filed Sept. 27, 1954 6 Sheets-Sheet 4 i INVENTOR a FRANK CARTL! DGE ATTORNEY Feb. 26, 1957 F. CARTLIDGE VARIABLE HEIGHT BORING TYPE CONTINUOUS MINING MACHINE Fil ed Sept. 27, 1954 6 Sheets-Sheet 5 I-NVENTO'R FRANK CARTLJDGE' ATTORNEY Feb. 26; 1957 F. CARTLIDGE 2,783,037

VARIABLE HEIGHT BORING TYPE CONTINUOUS MINING MACHINE Filed Sept. 27, 1954 6 Sheets-Sheet 6 FIG. .7

' INVENTOR 38 FRANK CARTUDGE FIG. 10 FIG- 9 BY 4322M M ZTTORN EY United States PatentO VARIABLE HEIGHT BORING TYPE CONTINUOUS MINING MACHINE Frank Cartlidge, Chicago, Ill., assignor to Goodman Manufacturing Company, Chicago, 11]., a corporation of Illinois Application September 27, 1954, Serial No. 458,494 13 Claims. (Cl. 262--7) This invention relates to improvements in multiple boring machines of the kind commonly known as McKinley type machines wherein two or more radial boring members are rotatable on parallel spaced axes to cut contiguous ovelapping bores in advance of the machine, and auxiliary cutter chains are guided horizontally by cutter bars immediately behind the boring members and trained around idler sprockets mounted at each end of the cutter bars sons to cut a substantially rectangular bore.

Since many mine roof conditions require timbering behind the mining machine, and quite close to the face, there must be some provision for collapsing the cutting ele ments when the machine is backed into the timbered part of the entry. The cutter bars are usually extensible and retractable vertically by power to facilitate withdrawal of the machine from the face and past the roof timbers, and means are also provided for inward swinging retraction of the cutter chain idler sprockets, thereby leaving sufiicient space at each side of the machine for timbering and for the operator.

A machine of the general type above described is shown in the copending'applications of James S. Robbins, bearing Serial Nos. 345,157 and 390,519, both owned by the assignee of the present invention, now Patent Nos. 2,745,- 649 and 2,745,648 respectively.

Since the thickness of height of a mine seam will vary from point to point it is advantageous that a continuous mining machine be provided with means to vary the cutting height so as to permit a maximum recovery of the coal or other mineral.

In the past, as shown for example in Cartlidge application Serial Number 431,454, filed May 21, 1954, on Boring Head for Mining Machines, variable height mining machines have included an adjustable boring head, the outer kerf cutting arms being adjustable radially from the hub rotational axis. In practice the range of this adjustability is limited since there is an optimum thickness of coal which can be broken off between the kerfs.

An object of this invention is to provide an improved construction in which the kerf cutting arms on the boring head may be kept fixed at the optimum radial spacing while retaining a wide range of height adjustment, the improvement specifically comprising an upper cutter bar which is vertically adjustable independently of the lower cutter bar in small increments above the paths of the outer kerf cutting arms on the boring heads.

Another object of this invention is to provide a'construction whereby a minimum of cutter chain take-up adjustment is required when the upper cutter bar is adjusted for varying heights of cuts, the cutter chain being driven from a fixed sprocket.

A further object of the invention is to provide means for producing a generally rectangular composite bore pat tern by the boring heads and the horizontal cutter bars which bore pattern has approximately vertical side wall portions along opposite ends of one or both of the cutter bars merging into the circular bores of the adjacent boring heads, so as to permit vertical timbering to be set closely ice adjacent the side walls of the composite bore, as well as to increase the amount of material removed by the machine. To this end, I provide cutter chain guide means adjacent the corner idler rollers, for guiding substantial lengths of the cutter chain in generally upright paths along opposite ends of one or both cutter bars, so as to produce generally rectangular, vertically sided kerf patterns at opposite ends of the cutter bar, which merge into the adjacent sides of the circular patterns cut by the boring heads, in all permissible positions of vertical adjustment of the cutter bar relative to said boring heads.

The invention may best be understood by reference to the accompanying drawings, in which:

Figure 1 is a side view of a continuous mining machine embodying a preferred form of the present invention;

Figure 2 is a front end view taken on line 22 of Figure 1, showing the machine in the lowest boring position in a mine, with roof-supporting timbers in place adjacent the working face, and with the upper and lower cutter bars, end sprockets and movable deflector plates disposed in fully extended normal cutting position, with certain parts broken away; g

Figure 3 is a view showing the pattern of the cores removed by the cu-tter chains while disposed as shown in Figure 2;

Figure 4 is a view similar to Figure 2, but showing the cutter bars, end sprockets and movable deflector plates in fully retracted position.

Figure 5 is a view similar to Figure 2, but showing the upper cutter bar raised to a higher cutter position;

Figure 6 is a view showing the pattern of the cores re moved by the cutter chains while. disposed as shown in Figure 5;

Figure 7 is a cross sectional view of the upper cutter bar taken generally along line 77 of either Figure 2 or Figure 5;

Figure 8 is an enlarged view of a portion of Figure 1, showing the linkage associated with the idler sprockets and guide rollers of the upper cutter bar in greater detail;

Figure 9 is a front view of one of the swinging members which are pivoted to the ends of the upper cutter bar and which carry the idler sprockets and guide rollers for the upper cutter chain;

Figure 10 is a left side view of the member shown in.

Figure 9;

Figure 11 is a bottom view of the member shown in Figure 9;

General description of machine Referring now to details of the embodiment of them- The auxiliary frarne23 is also arranged so that it may be; tilted forwardly or rearwardly by a pair of rearwardly in clined jacks 27. The gear casing 26 has extending forwardly therefrom a pairof laterally spaced power-driven shafts 28 which support boring members 29 arranged to rotate in timed relation to each other. The main frame- 21 has a longitudinally extending chain flight conveyor 31, as usual, for conducting fragmented material from the face through a throat 32 to the rear of the machine; The general arrangement of parts previously mentioned are substantially as described in the copending application of James S. Robbins, Patent No. 2,745,648, so need not be' .more fully described herein, excepting as to the features which form parts of the present invention.

Cutter chain drive ot: .theupper cutterchainmounted on the-upper: horizontal .cutteribar 34 .of the auxiliary frame, together with the .guidetmcans :for. said chains attheends of the uppercutter bar. In the form shownherein, a lower cutter:bar'35 supports a. separately driven cutterchain, as will hereinafter be morefully described.

Referring now toFigure 2, .anupper cutter chain 33 is trained along -.the'front of an upper cutter bar 34 which is mounted for vertical extension or retraction relative tot he auxiliary frame 23 by a'pair of hydraulic cylinders 41, 41, the piston rods 42,42 ofsaid cylinders being fixed to adjacent opposite ,ends of the cutter bar in the usual manner. The chain 33 is :suitably driven by a sprocket 43 onshaft44 extendingfrom thefront of the gear casing 26, substantially midway between the ends of the cutter bar 34..

From the drive sprocket 43 the upper cutter chain is trained over a tensioning roller 46,-slideably mounted on gear casing 26, thence overa guide roller 38 .andan end idlersprocket 36 at the leftendof the upper 'CllltEILbfll'34. After being guided along the cutter bane-side reach ofthe chain is trained over an end idler-sprocket 37 and guide roller 39 at the right end of said cutter bar, and a lower reach of the chain then extends over a guide roller 47 mounted on the gear casing 26, closely adjacent the drive sprocket 43. and thence to the drive sprocket 43. I The hydraulic cylinders 41 are bolted to machined pads 48 on the front face of the gear casing 26. In the form shown, the mounting pads are provided with a series of tapped holes 49 and the upper cutter bar 34, the idler sprockets 36 and 37, the idler rollers 38 and 39, and the associated members for extending and retracting the sprockets and rollers are all mounted for vertical adjustment. as a unit in increments of, say, 1 /2 inches as will hereinafter more fully appear to vary the cutting range of the upper cutter bar, in addition to its range of vertical movement due to the operation of the hydraulic cylinder 41. Figure shows the cylinders raised to their highest position. In this position the top cutter chain may be operating, say, 9 inches above the outer kerfs cut by the boring heads.

Bore producer] by rmlchl'ne in mine face When the upper cutter bar 34 is adjusted to its lowermost position, as shown in Figure 2, the boring members 29 and upper and lower cutter bars 34 and 35 cut a pattern in the mine face as the machine advances, which pattern is more or less diagrammatically shown in Figure 3, as will be seen in this figure, the two cutter bars are positioned respectively at the maximum diameter cut by the boring members 29.

Figure 6 shows more or less diagrammatically the pattern of the bore produced when the upper cutter bar 34- is raised to the fully extended cutting position shown in Figure 5. In practice, the upper core 51 is wedged downward by the inclined under faces 340 on the upper cutter bar 34 as the machine advances. The wedge shape of cutter bar 34 is shown in section in Figure 7. Knife edges 52, 52 are provided on the front of the piston rod mounting bosses 53, 53 of the upper cutter bar to help break up the core 51 shown at 54in Figure 6.

C urtingcleamnce for upper corner sprocket In the fully extended cutting position shown in Figure 5, the upper cutter chain end sprockets 36 and 37 are almost completely buried in the seam. Means of cutting d within the circular kerfis broken up by a small burster cone 58 similar to those employed on the boring heads. The cutter bits 56 and cones 58 are positively driven by their respective end sprockets 36 and 37.

Corner sprocket retracting and expanding linkage and associated mechanism .Since the sameform of linkage mechanism is used for both upper end sprockets, the description of the linkage associated with the .left end sprocket 36 (see Figures 2 and 5) of the upper cutter bar 34 will sutfice for an understanding of both linkages.

As shown generally in Figure 2, and in detail in Figures 9, l0 and I l the sprocket 36 is journaled on to a swinging link 59 shaped like a bell crank pivoted at its inner end by means of pivot pin 60 to an extension M at the left end of cutter bar 34. When the sprocket 36 is in its fully extended normal cutting position as shown inthis figure, the swinging link 59 extends angularly at an outward and then downward direction and the sprocket 36 is journalled at the angle of said link so that the top of the -sprocket is .in horizontal alignment with the cutter chain33 as .it passes along the cutter bar 34. The generally.vertical..downward extension 62 of the swinging .link 5.9 carries the roller 38 at its free end which guides the cutter chain, causing said chain to cut a substantially vertical rib at the upper corner of the bore (Figures 2 and 5 i.

The cutter bar 34 carries a depending bracket 63 at 3 its extreme left and to which is connected the swinging link 59 through two intermediate links 64 and 66 pivotally connected to each other at adjacent ends by pivot pin 67. In thefform shown the outer link 64 is a short link pivotally connected to the swinging link 59 approximately halfway between its point of pivotal connection with "the extension 61 and the journal of the sprocket 36. .As seen in Figure 8, the swinging link 59 is formed with integral furcations 59a and 59b between which the adjacent end of outer link 64 is connectedby pivot pin 68. The opposite end of outer link 64 is connected between furcations 66a and 66b formed on the adjacent end of inner link 66. The inner link 66 is pivotally connected at its lower end to a pin 69 mounted on the depending bracket 63.

An hydraulic cylinder 71, mounted between the inner link and the cutter bar 34 in a generally horizontal position, is employed to operate the linkage thereby extending and retracting the sprocket 36 and the guide roller 38 in a generally horizontal direction, in all positions of vertical adjustment of the cutter bar 34. The inner end of the cylinder is pivotally connected between a bifurcated bracket 72 on the cutter bar 34 by means of pin 73. The piston rod 74 is pivotally connected between furcations 66a and 66b of inner link 66 by the pivot pin 76.

Movable guide roller The location of the movable guide roller 38 allows said roller to-serve a threefold purpose. First, it guides the'upper cutter chain 33 so as to cut enough clearance for retraction 'of the idler sprocket 36. The end idler sprockets of the lower cutter bar 35 are buried in the seam no deeper than their axis of rotation and may be retracted without binding on the rib. The cutter bits 56 on upper end sprockets of the upper cutter bar 34, are designed to cut while completely buried in the seam when the upper cutter bar is in the extended position of Figure 6. If. the triangular core 77 (Fig. 6) were .noteut ed by the chain it would interfere with rotation of the sprocket 36 about pin (Fig 5) into the retracted position. Secondly, itguides the chain so as to cut a substantially vertical rib at 78 (Fig. 5), particularly desirable when the upper cutter bar is cutting in a relatively high level, thereby providing clearance for the upright timber 79. Thirdly, it allows a wide range of -vertical movement of the. upper cutter bar'with very little adjustment of-the chain tensioning roller 46. Referring now to Fig. 2, it will be seen that any required adjustment of the tensioning roller as the upper cutter bar is raised or lowered will occur dueto an increase or decrease in the distance between point A at the bottom of the left guide roller 38 to the point B at the top of the tensioning roller 46 and to an increase or decrease in the distance between point C at the bottom of the right guide roller 39 to the point D at the top of guide roller 47 on gear casing 26.

Referring now to Figure 6, it will be seen that the chain 33, represented by the dash-dot line, pivots about points B and D as the cutter bar is raised or lowered. The lines AB and A'B represent the positions of one inner reach portion of the chain in the lower and upper positions of adjustment of the cutter bar, while the lines DC and DC represent similar positions of the other inner reach portion of the chain. The algebraic summation of length A'B less AB and length CD less CD will give the change in effective length of chain required to maintain a substantially, uniform working tension. Such change may be accommodated by shifting the ten sioning roller 46 either upward or downward.

Since the idler rollers 38 extend the chain 33 downwardly at opposite sides of the cutter bar so that the points B and D are located approximately halfway between the limits of vertical movement of the points A and ,C, the adjustment of the tensioning roller 46 may be kept at a minimum, in all permissible positions of vertical adjustment of the cutter bar 34.

A somewhat similar linkage mechanism as just described is provided for the idler sprockets 82 and 83 on the lower cutter bar excepting that the chain guide roller 38 and its supporting arm 62 on swinging link 59 is absent. The form and arrangement of the linkage on the lower cutterbarare for illustrative purposes only, and form the subject matter of a copending application of Frank Cartlidge, Serial No. 459,443, filed September 30, 1954, now abandoned.

Referring now to Figure 2, a lower cutter bar 35 has a cutterchain 84 trained along its front edge. The lower cutter bar is mounted for vertical extension or retraction relative to the auxiliary frame, independently of theupper cutter bar 34, by a pair of hydraulic cylinders 87, 87 fixed on said frame having piston rods 88 fixed adjacent opposite ends of the lower cutter bar 35. In practice, vertical retracting of the lower cutter bar 35 is usually made use of only to facilitate transferring of .the machine from place to place in the mine.

The lower cutter chain 84 is suitably driven by a sprocket 89 on shaft 91 extending from the front of the gearcasing 26.

From the drive sprocket 89 the lower cutter chain 84 is trained over guide roller 92 and thence over the idler sprocket82 at the left end of the lower cutter bar 35. After being guided along the lower cutter bar, the chain is guided over idler sprocket 83 at the right end of said cutter .bar, thence over a guide shoe 93 mounted on the right hub 94 of the gear casing 26, thence over a tensioning idler 96, slidably mounted on gear casing 26, arid thence to thedrive sprocket 89.

Deflector plates The extending. and retracting linkages for the lower idler sprockets 82 and 83 carry. movable deflector plates 97 and 98 (shown at the right side of FigureZ) to insure that the cuttings, which fall from the boring members and ,the cutter chains. toward the mine floor, will be directed inwardly toward and through the open throat 32 for removal by the conveyor 31, and yet said deflector plates can be moved inwardly with the sprockets to facilitatewithdrawal of the machine from the working face. The form and arrangement of deflecting plates 97 and 98 shown herein are for illustrative purposes, and form the subject matter of a cdgending application 6 of Jerome C. Salmons, bearing Serial Number 408,003, filed February 3, 1954, owned by the assignee of the present invention, now Patent No. 2,719,709, so need not be further described herein, except to note that the upper portion 108 of the plate 98 is preferably made of a semi-pliable rubber sheet, so as to flex when the plates 97 and 98 are moved to the fully retracted position shown in Figure 4, to provide a maximum amount of lateral clearance if required, as for instance to pass by an upright prop .79, as indicated in the latterfigure.

Operation The use and operation of the machine is as follows:

Referring to Figure 2, the mining machine is represented as producing a bore in a working face. Figure 3 shows the bore produced which is defined by horizontal roof 109, floor 111 and side walls 112, 112 shaped with outwardly lowered intermediate portions 112a cut by the boring members 29, and smaller upper and lower lobes 11% and 112s cut respectively by the upper idler sprockets 36 and 37, and the lower idler sprockets 82 and 83, when the cutter bars are in normal cutting position as shown in Figure 2.

Inward retraction of the end sprockets is especially desirable to facilitate withdrawal of the machine from the face, as for instance when the operator wishes to perform adjustments on the boring members or cutter chains, or to tram the machine to another place in the mine. Also, undercertain mining conditions, roof props 79, 79 may be installed closely adjacent the rear of the end idler sprockets 36, 37 and 82, 83 in which case it would be impossible to withdraw the machine from the working face without retracting said end sprockets inwardly toward their respective cutter bars.

It will be seen from Figure 5, wherein the idler sprockets are fully extended into their normal cutting position, that the pivotal axes of the two links 64 and 66 of each idler sprocket linkage are held substantially in alignment with each other by the piston rod 74 of the hydraulic cylinder 71, thus providing in elfect a.

toggle arrangement to hold the swinginglink 59 in laterally extended position.

As will further be seen from Figures 5 and 6, that the corner sprockets 36, 37 and their respective guide rollers 38 depending therefrom on supporting arms 62, direct substantial lengths of the cutter chain 33 in generally vertical paths beyond the paths of movement of the adjacent boring heads, so as to cut substantially rectangular patterns having vertical side ribs at the upper corners of the composite bore produced by the machine, when the upper cutter bar is adjusted to an upwardly extendedposition relative to the boring heads.

It will also be observed by reference to Figure 6 that. the cutter chain 33 of the upper cutter bar 34 is driven independently of the cutter chain of the lower cutter bar 35, and that the drive sprocket 43 (Figure 2) for the upper cutter chain and the adjacent tensioning roller 46 constitute a chain guide means disposed on'the auxiliary frame below and approximately midway between. the ends ,of the upper cutter bar. The cutter chain guides carried by both ends of the upper cutter bar, including the end sprockets 36 and 37, and their depending guide rollers 38 on arms 62, are of such vertical length, as to extendthe cutter chain downwardly to a horizontal level approximately equal to the vertical distance betweenthe cutter bar and the drive sprocket, when the upper cutter bar is moved to levels between its maximum and minimum limits of vertical adjustment. Owing to this: novel arrangement, it has been found that a change of;

as much as nine inches in the vertical adjustment of the upper cutter bar 34, between its highest and lowest per? missible positions can be accomplished without requiring any change in adjustment of the tensioning roller 46,. and that a change of only one inch or less in vertical I adjustment of the tensioning roller 46 may be necessary when the cutter bar is moved to intermediate vertical positions. Accordingly, the novel relationship. between the length of the "supporting arm 62 for guide rollers '38 "andthe position of'the drive sprocket and tension roller just described'enormously simplifies the problem of maintainingproper tension on the cutter chain, as compared with previous cutter chain arrangements, wherein one or more 'tensioning devices, each having a range of several inchesgisnsually required fortension'rng the chain in various positions of vertical adjustment of the cutter bar.

When the .operator desires to withdraw the machine from the 'bore,"he may-operate a sequence valve of, any wellkn'own t'orrn (not shown) which first admits'hydraulicpressure to the rod side of the cylinders 71. Inward movement of the piston rod 74 serves to collapse the normal ia'ligned toggle arrangement oflliriks 64 and 66 so thatthe outer link '64 now assumes a downward and inward angle "and the inner link ,66 assumes an upward and inward angle, with the result that the link 59 and sprocket '36 are forced to swing downwardly and inwardly to a retracted position as shown in Fig. 4. The extension 62 of swinging link 59 which carries the guide roller 38 assumes a generallyhorizonta'l inwardly extending position adjacent the'lower edge of the upper cutter bar 34. In this position, the guide roller, sprocket and chain are brought within the lateral limits of the gear-casing 26,:affording ampleclearance from the adjacent side 'wall 112 of the bore, and also an upright mine prop 79,.if the latter is used asshown.

After thesprockets are retracted the above-mentioned sequence valve admits hydraulic pressure to the rod side ot'the cylinders 41, 41 and'87, 87, therebylowering the upper cutter bar 34 and raising the lower cutter bar 35, affording enough vertical clearance to movetthe machine pastthe roof supporting ti1riber'113, as shown in Fig. 4.

If it becomes desirable to change the height of the bore, the operator merely removes thebolts holding the upper cylinders 41 to the gear casing 26, remounts the cylinders in a different position, such as that shown in Fig. 3, and readjusts theteusioning roller 46 to the proper tension, if necessary.

It-willnow be understood from the above description that the novel linkages for extending and retracting the idler sprockets 36 and 37 and the guide rollers 38 and 39-and the means for operating said linkages are both carried by the upper cutter bar '34, making the entire unit. easily detachable .and vertically adjustable over a wide range. Also, the design of the sprockets 36 and 37 and the location of the guide rollers 38 and 39 'permit the upper cutting chain assembly to be raised-above the lt'erfs cut by the boring heads Where said assembly will cut itsown clearance.

Although I have shown and described certain embodiments of my invention, it will be understood that I do notwish to be limited to the exactconstruction shown and described'but that various changesand modifications may be made without departingfrom.thespirit and scope of the invention as defined in the appended claims.

i claim:

l. in a mining machine, a frame having a plurality of boring heads rotating in side-by-side relation to produce contiguous bores in advance of the machine, and horizontally disposed upper andtlower cutter :chain carrying cutter bars disposed rearwardly of said boring heads for-extending the bore pattern formed by said boring heads, the oppositcendr. of the (upper cutter bar extending laterally beyond the centers of rotation-of said bor ing heads and having cutter chain guide means at oppo site cndsthereof, including corner guidestor the cutter chain. and generally upright guide means disposed along opposite ends of the upper cutter bar, with their lower ends terminating "substantially within the bore pattern of.'the adjacent boring heads, and spaced vertically from the. lower cutter bar to guide side reach portions .of said cutter chain along extended rectilinear uprightpaths for producing substantially rectangular corner patterns at opposite ends ofv said upper cutter bar merging into the circular pattern atoppositeysides of :the adjacent boring heads.

.2. The structure of claim 1, wherein the upright guide means along opposite ends of the uppercutter bar .include corner sprockets, and idler rollers spaced vertically below the corner sprockets, the :idler rollers being disposed within the bore pattern of the adjacent boring head.

3. The structure of claim 1, wherein the upper cutter bar is adjustable to horizontal cutting planes above the vertical cutting limits of the boring heads, and the upright cutter chain guide means at opposite ends of the cutter bar merge into the circular pattern of the adjacent boring .heads in all permissible positions of adjustment of the cutter bar.

4. The structure of claim '1, .wherein the upper .cntter bar has limited vertical adjustment to various Jhorizonta'l levels relative to the boring heads, and the cutter chain thereon is driven from means includingadrive sprocket and guide means disposed centrallyof'the frame approximately equidistant from the ends of the cutter bar and approximately at the'level of the -lower ends of the upright guide means on the cutter bar, when the cutter bar is disposed at a level approximately midway between its maximum and minimum limits of vertical adjustment.

5. In a mining machine, a frame having a plurality of boring heads rotatable in sideby-sid e relation to produce bores in advance of the machine, "horizontally disposed upper and lower cutter chain carrying cutter bars disposed 'rearwardly of said'boring heads for extending the bore pattern formed by said boring heads, cutter chain guide means mounted on said frame, the upper cutter bar being vertically adjustable relativeto the cutter chain guide means on the 'frame,and having depending direction changing elements atits opposite ends, a cutter chain guided along said upper cutter bar and. about said direction changing elements, and with inner reach portions extending between said direction changing elements and the guide means on the frame in generally horizontal directions, and at least one of ,saidfinnerreach portions being movable between positions above and below a horizontal plane including ,the lower extremity of its adjacent direction changing element when said upper cutter bar is adjusted verticallybetween its uppermostand lowermost positions.

6. In a mining machine, a frame having .a plurality ofboring heads rotatablein side-byside relation to'.produce bores in advance of the machine, horizontally dis posed upper and lower cutter chain carrying cutter bars disposed rearwardlyof said boring heads for extending the bore pattern formed by said'boringheads, .saidframe having cutter chain driving sprocket means and cutter chain slack take-up means mountedthereonatfixed locations intermediatethe ends ,of thewuppercuttertbar, the upper cutter bar being verticallyadjustable relative to said frame and having dependingnditectionchanging elements at its oppositeends, acuttermchain guidedalong said upper cutter bar and about said direction changing elements, and with one inner reach portion extending between said sprocket-means and its adjacent direction changing element on the upper cutter bar audanother inner reach portion extendingbetween said-slacktake-up means and its adjacent directionchanging .element .on the upper bar, both of .said inner reach portions being movable above and below a horizontal plane-including the lower extremities of their adjacent direction chang ing elements to minimize changein .the-total length of the cutter chain when the upper cutter-bar .is vertically adjusted between its uppermost and lowermost positions.

7. jin a mining machine, a framenhavinga boring head etiectiveto produce a bore in amine face .in advance of the machine, a horizontally disposed cutter bar carried by said frame having depending direction changing elements at opposite ends thereof, said cutter bar being adjustable vertically relative to said frame between a collapsed position and an extended position, cutter chain guide means mounted at a fixed location on said frame intermediate the ends of said cutter bar, and including at least one driving sprocket, said cutter chain having two inner reach portions extending oppositely from said guide means to the direction changing elements at the opposite ends of said cutter bar, both of said reach portions extending in a direction generally parallel to said cutter bar, and at least one of said inner reach portions being movable with said cutter bar between positions on opposite sides of a horizontal plane including the lower extremity of the adjacent direction changing element on said cutter bar.

8. In a mining machine, a frame having at least one boring head rotatable to produce a bore in advance of the machine, and at least one cutter chain carrying cutter bar disposed rearwardly of said boring head for extending the bore pattern formed by said boring head, at least one end of said cutter bar extending laterally beyond the extremity of said boring head and having cutter chain guide means thereon including a power driven rotatable, direction-changing element about which the cutter chain is trained, and cutter bit means on the forward portion of said rotatable element for cutting clearance in the mine face laterally beyond the bore cut by the head.

9. In a mining machine, the combination recited in claim 8 in which the rotatable direction changing element is driven by the cutter chain.

10. In a mining machine, a frame having a plurality of boring heads rotating in side-by-side relation to produce contiguous bores in advance of the machine, and horizontally disposed upper and lower cutter chain carrying cutter bars disposed rearwardly of said boring heads for extending the bore pattern formed by said boring heads, the opposite ends of at least one of said cutter bars extending laterally beyond the extremities of said boring heads and having cutter chain guide means at opposite ends thereof including sprockets for the cutter chain, and cutter bit means on the forward portions of said sprockets for cutting clearance for said sprockets in the mine face laterally beyond said contiguous bores.

11. In a mining machine having a frame with a plurality of boring heads rotating in side-by-side relation to produce contiguous bores in advance of the machine, a horizontal cutter bar disposed rearwardly of said boring heads for extending the bore pattern formed by said boring heads, means for vertically extending or retracting said cutter bar relative to said frame, levers pivotally supported in generally depending relation at opposite ends of said cutter bar for retraction inwardly below to said bar, each of said levers having a corner guide adjacent its upper end for normally supporting the cutter chain in horizontal alignment with the cutter bar when its lever is in normal extended position, and each of said levers also having a terminal guide at its free end, said corner guides and terminal guides being arranged to support substantial reaches of the cutter chain in generally vertical paths disposed laterally beyond the paths of movement of the bore pattern formed by the adjacent boring heads, when said levers are in their normal extended positions, and said corner guides and terminal guides being pivotally retractable inwardly with their respective levers to positions substantially within the bore patterns of the adjacent boring heads. 12. The structure in accordance with claim 11, Wherein each of the corner guides consists of a sprocket rotatably supported on its respective link, and driven by the cutter chain.

13. The structure in accordance with claim 12, Wherein each of the levers is in the shape of a bell crank having one end pivotally mounted on the adjacent end of the cutter bar, with its terminal chain guide mounted on its free end, and its corner sprocket journalled thereon intermediate its ends.

References Cited in the file of this patent UNITED STATES PATENTS 1,603,621 McKinlay Oct. 19, 1926 2,093,448 Joy Sept. 21, 1937 2,705,624 Robbins Apr. 5, 1955 2,711,889 Robbins June 28, 1955 2,719,710 Ogden Oct. 4, 1955 FOREIGN PATENTS 496,181 Belgium Oct. 2, 1950 

